Soft thermoelectrics provide the unique opportunity to combine traditional thermoelectric energy generation with inexpensive processing methods, tunable chemistries, and flexible form factors, opening the door to previously unattainable device architectures and applications. Traditional inorganic thermoelectrics are restricted by rigid geometries and use of expensive components with low earth abundance. The performance of thermoelectric materials is commonly characterized by a dimensionless figure of merit ZT=S2σT/κ. For a given temperature T, this figure of merit depends on three material properties: the Seebeck coefficient S, electrical conductivity σ, and thermal conductivity κ, which are inherently coupled in band conduction materials, limiting optimization.
In contrast, organic and organic—inorganic composite thermoelectrics possess both inherently low thermal conductivities and unique thermal and electrical transport mechanisms, attributes which enable new strategies to break traditional performance optimization boundaries. Recent progress on soft thermoelectrics has been rapid, and performance of these materials is approaching that of traditional inorganics. However, the advantages of soft thermoelectrics extends beyond electronic properties—by leveraging tunable form factors along with these striking performance gains, researchers have successfully provided proof of principle for novel thermoelectric device architectures such as flexible modules and wearable thermoelectric fabrics. Morphological and architectural control over these materials provides another crucial mechanism for controlling transport in soft materials and invites new possibilities for reimagining soft thermoelectric applications.